A laser is a device which has the ability to produce monochromatic, coherent light through the stimulated emission of photons from atoms, molecules or ions of an active medium which have typically been excited from a ground state to a higher energy level by an input of energy. Such a device contains an optical cavity or resonator which is defined by highly reflecting surfaces which form a closed round trip path for light, and the active medium is contained within the optical cavity.
If a population inversion is created by excitation of the active medium, the spontaneous emission of a photon from an excited atom, molecule or ion undergoing transition to a lower energy state can stimulate the energy of photons of substantially identical energy from other excited atoms, molecules or ions. As a consequence, the initial photon creates a cascade of photons between the reflecting surfaces of the optical cavity which are of substantially identical energy and exactly in phase. A portion of this cascade of photons is then discharged out of the optical cavity, for example, by transmission through an output coupler. These discharged photons constitute the laser output.
Excitation of the active medium of a laser can be accomplished by a variety of methods. However, the most common methods are optical pumping, use of an electrical discharge, and passage of an electric current through the p-n junction of a semiconductor laser. Semiconductor lasers contain a p-n junction which forms a diode, and this junction functions as the active medium of the laser. Such devices are also referred to as laser diodes. The efficiency of such lasers in converting electrical power to output radiation is relatively high, and for example, can be in excess of 40 percent.
Small angular misalignments of optical components of a laser can result in substantial losses in laser output power. Accordingly, laser resonators are designed to ensure the maintenance of a stable orientation of these optical components. Ambient temperature fluctuations and temperature fluctuations produced as an undesired by-product of laser operation have also placed constraints on the design of laser resonators. These temperature fluctuations can result in thermally induced distortions of the resonator and associated misalignment of the optical components within the resonator. Accordingly, conventional laser designs have addressed this problem through the use of materials having a low coefficient of thermal expansion, such as Invar, quartz and various ceramics, and also by using external cooling means to thermally stabilize the resonator.
U.S. Pat. Nos. 4,730,335 and 4,731,795 both issued to Clark et al. on Mar. 8, 1988 and Mar. 15, 1988, respectively, are directed to optically pumped solid state lasers which are constructed of components held in association by support structures which are configured to receive the components and automatically arrange them with respect to one another along an optical path.
In the past, aluminum barrels have been commercially used to align and house optical components such as lenses and lasant materials. These barrels require a spacer between the lens and lasant material, and the various optical components must be inserted and adhesively bonded to the inside of the barrel. The drawbacks of such barrels include, for example, a significant likelihood of assembly error (i) by contaminating one of the optical component surfaces by misapplying or improperly spreading the adhesive thereon, or (ii) by damaging, chipping, cracking, scratching, etc., upon insertion into the barrel, one of the optical components, each of which can severely affect the output power or cause total failure of a laser. Accordingly, the components must be inserted carefully into the barrel apparatus, thus requiring manual insertion which is unadaptable to mass production. Another limitation of the barrel apparatus, is that once the lens and lasant material are adhesively bonded to the barrel, if either component has a surface contaminant or defect, the other non-defective component cannot be readily reclaimed. The barrel has to be cut or machined open to reclaim the non-defective component. In such circumstances, it may be more cost effective simply to discard the barrel with the components therein, rather than attempt to reclaim the non-defective component.